1. Technical Field
The present invention relates generally to protective shelters, and more particularly to redeployable mobile aboveground shelters using ducting (with and/or without unidirectional check valving) and/or retractable stabilizers to resist movement during high velocity wind events.
2. Description of the Related Art
The construction of storm shelters, safe rooms and blast resistant modules is well known and thoroughly documented, for example, in FEMA 320, Third Edition and FEMA 361, Second Edition, both available from the Federal Emergency Management Agency (FEMA), as well as in ICC/NSSA 2008 “Standard for the Design and Construction of Storm Shelters,” published jointly by the International Code Council (ICC) and the National Storm Shelter Association (NSSA) and in Section 6, Wind Loads, of “Minimum Design Loads for Buildings and Other Structures,” SEI/ASCE 7-05, 2005, ISBN: 0-7844-0809-2, published by the American Society of Civil Engineers. To meet safety standards, conventional shelters require either burial below ground or, for aboveground shelters, secure fastening of the shelter by numerous metal bolts or adhesives to heavy foundations or concrete “pads”. For aboveground shelters, the combined weight of the shelter plus its foundation or “pad” is the primary factor relied upon to resist movement of the shelter (and thus provide protection of its occupants) during high velocity wind events. In virtually all instances non-residential aboveground shelters are designed to be permanently installed at one location.
The unavailability of redeployable or mobile protective shelters leaves at risk personnel that are temporarily located where severe wind events may occur. Those working on oil well drilling rigs, pipeline construction, wind turbine erection, petroleum refineries, compressor station repair, and road construction and repair are examples of personnel at risk. One of the challenges of providing severe wind event protection for such personnel is the need for the shelter to be able to be easily, quickly and inexpensively relocated to different work sites as the crews frequently relocate.
Conventional above ground protective shelters depend almost completely upon the total weight of the shelter and its attached concrete foundation to resist movement. To a lesser degree, the large width of the required concrete foundation also helps the assembly resist overturning. To resist wind induced overturning, uplift and sliding, some shelters require the use of expensive subterranean concrete footings in addition to the wide width and massive weight of the foundational pads. Although pre-cast concrete community and industrial shelters are available, their immense weight (approximately 75,000 lbs. or more) requires the use of specially permitted and oversized trucks to haul them and heavy cranes to lift them into place, which renders their temporary redeployment impractical. Some conventional metal shelters can be unbolted from their heavy concrete bases and moved more easily. However, each new location requires the preparation of another heavy concrete pad to which the shelter can be bolted. In most instances the cost and inconvenience of pouring of a new pad (and the attendant environmental impact of their subsequent demolition and removal) renders impracticable the redeployment of a metal protective shelter for temporary use.